A colorimetric and fluorescent dual-channel cyanide ion probe using crosslinked polymer microspheres functionalized with protonated Brooker's merocyanine

Origin of Spectral Features and Acid–Base Properties of 3,7-Dihydroxyflavone and Its Monofunctional Derivatives in the Ground and Excited States

“…Organic fluorophores in which the excited-state proton transfer (ESPT) occurs have been shown to be useful spectral indicators in various chemical, environmental, − and biological investigations. − The use of the compounds in this role emerges from their ability to occur in the electronically excited state in various structural forms (tautomeric, rotameric, protolytic) each of which have different fluorescent features (emission wavelengths, lifetimes) which depend on the properties of the medium (such as polarity, acidity/basicity, hydrogen-bonding ability) or biological environment. One group of compounds that are widely used as ESPT fluorophores are hydroxyflavones (hydroxy-2-phenyl-4 H -chromen-4-ones), − which represent the target compounds in the present investigation.…”

“…The absorption of radiation by the neutral forms N of the compounds investigated lead to the electronically excited N * form which in the case of 1 and 3 undergo ESIPT to produce a thermodynamically more stable T 3 * form (Table 4, (Table 3), protolytic dissociation of N * to A 7 * is also a thermodynamically spontaneous process; however, the intramolecular tautomeric transformation N *  T 3 28 by the scheme: N *  T 3 *  A 7 T *  A 7 * (Scheme 3), which explains the presence of monoanionic forms of the compound under these conditions. In the case of compound 2, dissociation of N * (which is formed as a result of the absorption of radiation by neutral molecules) and T 7 * (which is generated via protolytic dissociation of electronically excited cations) to A 7 * occurs in medium acidic media ( Figure 4, Table 3).…”

Optical Chemosensors and Chemodosimeters for Anion Detection Based on Merrifield Resin Functionalized with Brooker’s Merocyanine Derivatives

“…Brooker’s merocyanine (BM) is a classical merocyanine which has been extensively used as a perichromic dye. − This dye has been employed in many strategies for the development of optical devices for the detection of anionic species. − The use of this system in an acid–base approach has been demonstrated, since the compound in its protonated form (BMH) is colorless in solution but can be deprotonated in the presence of basic anionic species, such as CN – or F – , in organic solvents to form the deprotonated form (BM), which is colored in solution (Scheme ). , Another strategy involves the use of BM as an indicator in displacement assays for the detection of anionic species. ,, A chemodosimeter approach can also be designed, in principle, using BM as a signaling unit, inspired by recent work reported in the literature, where the classical protection reaction was used for the silylation of phenols to yield colorless systems.…”

Rigidified Push–Pull Dyes: Using Chromophore Size, Donor, and Acceptor Units to Tune the Ground State between Neutral and the Cyanine Limit

“…Furthermore, they were used as optical sensors to monitor the composition and phase structure of lipids by absorption and emission spectroscopy, and to study transmembrane electrical heart activity, brain plaque, as well as leukemic cells . More recently, merocyanines have been used as chemosensors, for example, in the colorimetric detection of cyanide ions and for determination of the water content in organic solvents . Furthermore, push–pull dyes feature promising second‐order nonlinear properties making them interesting candidates for electronic and optoelectronic applications …”